This invention relates to edible oils containing omega-3-fatty acids, in particular eicosapentaenoic acid (EPA). The invention also relates to methods of producing EPA in commercially viable yields.
Omega-3-fatty acids are known to be beneficial in reducing the incidence of coronary heart disease. The metabolism of omega-3-fatty acids is not understood. Thus, although these acids are known to have beneficial effects, precise clinical dosages and efficacy are not known.
Omega-3-fatty acids, including EPA, have been found in the oils of cold water marine fish. Indeed, this is the primary source of commercially available EPA. It is believed that the omega-3-fatty acids found in fish originate from phytoplankton which are at the base of the marine food chain. The belief is due to the fact that many phytoplankton species are found to contain reserves of oil containing varying amounts of EPA.
Certain marine microorganisms are known to contain EPA. For example, Yazawa et al., J. Biochem, 103:5-7 (1988), found 88 strains of gram-negative bacteria which produced EPA. U.S. Pat. No. 4,615,839 (Seto et al.) discloses the cultivation of monocellular green algae in open pools followed by recovery of EPA from those microalgae.
While omega-3-fatty acids are known to have medicinal utility, there are problems associated with their use. Because of their association with fish oils, there is often a fishy odor and unpleasant taste associated with these acids. Additionally, although fish oils do contain EPA, many of these oils cannot be consumed by humans due to the presence of attendant contaminants, such as PCB, as well as a high concentration of oxidation-sensitive polyunsaturated fatty acids, some of which exhibit bioactivities which are different from, and even antagonistic to, EPA. Furthermore, oils from many fish, particularly fish from tropical zone waters, also contain significant quantities of arachidonic acid which exhibits a biological effect antagonistic to EPA. While production of omega-3-fatty acids in microorganisms would eliminate the contaminant problems, no commercially acceptable and economically feasible method of producing large quantities of these acids in microorganisms has been available.
Isotopically labelled EPA would be of great benefit in elucidating the pathway of omega-3-fatty acid metabolism. However, labelled EPA in sufficient quantities to perform such research has not heretofore been obtainable.
Accordingly, it is an object of the present invention to produce EPA in microorganisms by a commercially feasible method to obtain commercially acceptable yields.
Further, it is an object of the present invention to produce isotopically labelled EPA from this cultivation process in amounts sufficient to study omega-3-fatty acid metabolism.